摘要:

Due to the abrupt increase in 2,3-diphosphoglycerate (2,3-DPG) concentration in the newborn lamb, which begins soon after birth, this interval in development was considered an excellent period to test the hypothesis that glucose perfusions could inhibit 2,3-DPG synthesis. Ten newborn lambs were divided into two groups and perfused either with glucose (15 mg/kg/min) or physiologic saline (45% NaCl) for 10 days. Blood gases, electrolytes, glycemia, O2pressure at 50% Hb saturation, and 2,3-DPG levels were compared in the two groups. Glucose levels remained significantly elevated during the first 3 days in the glucose perfused group. The O2pressure at 50% Hb saturation increased in both groups but was significantly lower in the glucose perfused group when determined on day 5 and 8. The postnatal increase in 2,3-DPG was significantly diminished in the glucose infused lambs, which suggests that glucose perfusion has an inhibiting effect on erythrocyte 2,3-DPG synthesis. (Pediatr Res24: 470–472, 1988)

ISSN:0031-3998    

出版商:OVID    

年代:1988

数据来源: OVID

摘要:

Interest in the pathogenesis of neonatal necrotizing enterocolitis has prompted study of the intestinal circulation in developing animals. It is conceivable that poorly developed collateral channels may predispose the neonatal intestine to ischemic insults. We therefore characterized intestinal collateral blood flow in anesthetized and ventilated 1-day and 1-month-old piglets. Intestinal blood flow was measured with radioactive microspheres (15 μm diameter) before and after either1) total occlusion of the superior mesenteric artery (SMA) or2) occlusion of a distal (jejunoileal) branch of the SNIA. After total SMA occlusion in 1-day and 1-month-old piglets, perfusion of the intestine via collaterals from the celiac and inferior mesenteric arteries was not evident. Jejunal, ileal, and colonic (except rectal) blood flows fell to zero 30 min after ligation of the SMA. Ligation of a distal branch of the SMA in 1-month-old animals significantly reduced total wall (by 25%) and mucosal/submucosal (by 25%) blood flows in the occluded segment. Similar experiments in 1-day-old piglets produced significantly greater reduction in total (70%) and mucosa/subumeosa (70%) blood flows. Muscle/serosa blood flows in both groups were not significantly different from control values. In conclusion, collateral perfusion of the intestine via the celiac and inferior mesenteric arteries is insignificant during acute SMA occlusion in the developing piglet. Although there is significant collateral blood flow within the SMA vascular network, perfusion between adjacent gut segments is less effective in preventing intestinal ischemia after occlusion of a branch of the SMA in neonates than in 1-month-old piglets. (Pediatr Res24: 473–476, 1988)

ISSN:0031-3998    

出版商:OVID    

年代:1988

数据来源: OVID

摘要:

Thirty-three premature and full-term infants (31.5–50 wk postconceptional age) free from neurologic and cardiopulmonary disease at time of testing, underwent a standardized ocular compression test during polygraphically controlled rapid eye movement sleep. RR intervals were measured on the ECG before and during ocular compression. RR interval changes during ocular compression were compared to the preceding 60-s mean RR interval in each infant. Results were analyzed relative to gestational age, postnatal age, and postconceptional age. Baseline heart rate during REM sleep decreased with postconceptional age. During ocular compression, there was a significant negative correlation between the longest RR interval or the “latency” variable with postconceptional age. Latency is defined as the time, in milliseconds, from beginning of eyelid pressure to the first measurable RR increase compared to mean control RR + 1 SD. Our results indicate that during rapid eye movement sleep, “baseline heart rate” decreases with maturation, an effect supposedly related to increased vagal activity, whereas the heart rate response on ocular pressure stimulus, a vagally mediated reflex, is significantly influenced and blunted with maturation. (Pediatr Res24: 477–480, 1988)

ISSN:0031-3998    

出版商:OVID    

年代:1988

数据来源: OVID

摘要:

Uptake of retinol in the developing intestine of suckling rats (14–15 day old) and its maturation in adult rats (90 day old) was examined using intestinal everted sacs. Uptake of retinol (0.06 μM) in the jejunum of suckling and adult rats was linear for 5 min incubation and occurred at a rate of 31.20 and 6.98 pmol/g tissue/min, respectively. In both age groups, uptake of retinol (0.06 μM) was significantly higher (p< 0.01) in the jejunum than the ileum. Uptake of retinol was significantly higher (p< 0.01) in suckling rats as compared to adult rats both in the jejunum and the ileum. In both suckling and adult rats, the uptake of retinol in the jejunum was1) saturable with a Vmaxvalue of 19.78 and 6.24 nmol/g tissue/5 min and an apparentKmvalue of 16.20 and 8.19 μM, respectively,2) not affected by metabolic inhibitors, and3) partially temperature dependent (Q10= 2.51 and 1.92, respectively). The structural analogues retinal (50 μM) and retinoic acid (50 μM) did not affect the uptake of [3H] retinol (0.06 μM) whereas unlabeled retinol (50 μM) caused significant (p< 0.01) inhibition. No difference in retinol metabolism by intestinal tissue was observed in the two age groups. These results demonstrate that retinol uptake in suckling rats is similar to that of adult rats in being a passive carrier-mediated process. The results also suggest that a decrease in the number and/or activity and an increase in the affinity of the uptake system of retinol occurs with maturation. (Pediatr Res24: 481–485, 1988)

ISSN:0031-3998    

出版商:OVID    

年代:1988

数据来源: OVID

摘要:

Our study tests the hypothesis that hyperviscosity independent of arterial O2content reduces cerebral cortical blood flow, O2delivery, and O2uptake. After baseline determinations, ten 2− to 4-day-old awake spontaneously breathing piglets were given an intravenous infusion (5 mlkg-1, body weight) of concentrated cyroprecipitate, whereas eight controls received normal saline. Cerebral cortical blood flow, arterial and superior sagittal sinus O2content, whole blood viscosity, hematocrit, blood gases, and plasma fibrinogen concentrations were measured at baseline and 3 h after infusion. No significant changes were observed in the control group. Three hours after the infusion of concentrated cryoprecipitate the experimental group showed an increase in whole blood viscosity, whereas hematocrit and arterial O2content were unchanged. There was a decrease in cerebral cortical blood flow and cerebral cortical O2delivery, whereas cerebral cortical O2uptake was unchanged. We conclude that hyperviscosity independent of arterial O2content reduces cerebral cortical blood flow and that although O2delivery was reduced in the newborn piglet cerebral cortical O2uptake was maintained. (Pediatr Res24: 486–489, 1988)

ISSN:0031-3998    

出版商:OVID    

年代:1988

数据来源: OVID

摘要:

To assess the value of cord plasma arginine vasopressin (AVP), erythropoietin (EP), and hypoxanthine (HX) as indices of asphyxia, we studied 62 infants of mothers with preeclampsia, 34 acutely asphyxiated infants, with 5-min Apgar score 6 and/or umbilical arterial pH 7.05, and 38 control infants. Umbilical arterial AVP in the asphyxia group (geometric mean; 95% confidence interval: 180; 92–350 pg/ml) was higher than in the control group (23; 8–466,p= 0.002) and correlated with umbilical arterial pH (r= −0.447,p= 0.028). AVP levels in the preeclampsia group did not differ from controls. Cord venous EP was higher in infants delivered by elective cesarean section from women with severe preeclampsia (115; 75–177 mU/ml,p< 0.001) than in control infants (23; 18–27); in the whole group EP correlated with pH (r= −0.493,p< 0.001). EP in the asphyxia group was similar (46; 35–65) to controls (40; 33–47) and did not correlate with pH. Cord arterial HX in the preeclampsia group was similar to controls (12.3; 9.5–16.0 μmol/liter), but elevated in the asphyxia group (23.7; 17.6–31.8,p= 0.001), in which HX correlated with pH (r= 0.558,p= 0.008) and AVP (r= 0.588,p= 0.005). EP did not correlate with AVP or HX in any group, nor did any of the variables correlate with the Apgar score. We conclude that cord plasma AVP and HX reflect acute asphyxia, whereas EP is elevated after more prolonged hypoxia. (Pediatr Res24: 490–494, 1988)

ISSN:0031-3998    

出版商:OVID    

年代:1988

数据来源: OVID

摘要:

The abnormalities in ion transport in cystic fibrosis (CF) respiratory and sweat duct epithelia have prompted studies of ion permeability in CF red blood cells (RBC) although previous reports have been contradictory. In this study, the kinetic characteristics of the three major cation transport systems in RBC were evaluated by measuring rubidium (Rb) uptake at various external Rb concentrations. The maximal velocity and affinity for external Rb (K1/2) of the NaK pump were normal in CF RBC, as were the maximal velocity andKmfor Rb of the NaK cotransport system. Residual (ouabain and bumetanide insensitive) Rb uptake, and steady state RBC Na and K contents were also normal. These data indicate the NaK pump and cotransport system do not exhibit primary or secondary perturbations in CF RBC, and suggest that the noncarrier-mediated membrane permeability to cations is also normal in these cells. (Pediatr Res24: 495–498, 1988)

ISSN:0031-3998    

出版商:OVID    

年代:1988

数据来源: OVID

摘要:

The renin-angiotensin system is activated by congestive heart failure associated with a ventricular septal defect (VSD). To determine the effect of angiotensinconverting enzyme inhibition on the hemodynamics with VSD, the dose response curve of captopril was measured in lambs. Furthermore, the effect of captopril on the distribution of systemic output was determined by the radio-nuclide-labeled microsphere technique. A total of 12 lambs (less than 1 month old) with VSD were instrumented and a minimum of five animals was tested for each data point. Captopril (0.05–10 mg/kg) caused dose-dependent vascular changes. At a dose of 2 mg/kg, maximal hemodynamic effects were observed. The systemic resistance fell by 28 ± 9% (mean ± SD,p< 0.05,n= 9), whereas pulmonary arteriolar resistance rose by 113 ± 34% (p< 0.05). These vascular changes caused a reduction in the ratio of pulmonary to systemic flow from 3.31 ± 0.59 to 2.19 ± 0.29 (-34%,p< 0.05) and a reduction in left-to-right shunt volume by 30% (p< 0.05). The left atrial pressure fell from 17.3 ± 3.4 to 10.8 ± 2.8 mm Hg (-38%,p< 0.05). Mean aortic pressure was unchanged (71.2 ± 8.1versus67.4 ± 9.1). Forward flow from the left ventricle increased from 2.17 ± 0.46 to 2.86 ± 0.54 liter/min/M2(p< 0.05). Microsphere-determined organ blood flow to the heart, kidney, liver, duodenum, and skeletal muscle was preserved after a 5 mg/kg dose of captopril and, in fact, tended to increase, but the changes were not significant. The myocardial endocardial to epicardial flow ratio increased from 1.17 ± 0.27 to 1.49 ± 0.14 (+27%,p< 0.05). The data indicate that captopril caused dose-dependent changes in the distribution of left ventricular output in lambs with VSD, reducing total pulmonary flow while preserving organ blood flow. (Pediatr Res24: 499–503, 1988)

ISSN:0031-3998    

出版商:OVID    

年代:1988

数据来源: OVID

摘要:

Samples of nasopharyngeal secretions from a group of 73 infants with bronchiolitis or upper respiratory illness alone during infection with respiratory syncytial virus were analyzed for leukotriene C4(LTC4) content using a reverse-phase high-pressure liquid chromatography assay with confirmation by radioimmunoassay. Titers of respiratory syncytial virus (RSV)-specific IgE in nasopharyngeal secretion (NPS) specimens were determined using an enzyme-linked immunosorbent assay. The highest concentrations of LTC4were found in the first 3 to 8 days after the onset of illness, and LTC4was detectable in progressively lower concentrations in samples obtained up to 28 days after the onset of illness. LTC4was detected in samples of NPS obtained in the acute phase of illness from 67% of infants with bronchiolitis due to RSV and in 33% of samples of NPS obtained during the same interval from infants with upper respiratory illness alone (p< 0.025). Concentrations of LTC4in children with bronchiolitis were 5-fold higher (1271 pg/ml) then the mean concentration of LTC4in children with upper respiratory illness (224 pg/ml,p< 0.02). LTC4was detected in 83% of the children developing an RSV-IgE response and in 24% of subjects not developing an RSV-IgE response (p< 0.001). Quantities of LTC4measured in NPS were directly correlated with the magnitude of the RSV-IgE response in secretions (r= 0.33,p< 0.02). These studies lend support to previous investigations suggesting that severe bronchiolitis due to RSV results from IgE-mediated hypersensitivity reactions to viral antigens, with release of chemical mediators of airway obstruction. Their implications should be considered in new approaches to therapy of RSV bronchiolitis. (Pediatr Res24: 504–507, 1988)

ISSN:0031-3998    

出版商:OVID    

年代:1988

数据来源: OVID

摘要:

The adherence of radiolabeled fimbriated (S 7471 ØF) and nonfimbriated (S 7471 N)Salmonella typhimuriumto small intestinal rat enterocytes was examined during postnatal development. The fimbriated strain invariably adhered in higher numbers than the nonfimbriated strain during all periods of development. The capability of enterocytes to bind Salmonella increased significantly during postnatal development and reached adult levels at weaning time (21 days of age). Bacterial adherence to enterocytes was similar if the cells were isolated from the proximal or the distal small intestine. Early weaning of pups did not affect the capability of enterocytes to bind Salmonella. Pretreatment of isolated enterocytes from adult animals with rat's milk before exposure to Salmonella had no effect on the level of bacteria that adhered per enterocyte. Conversely, pretreatment of Salmonella with rats' milk before binding to enterocytes from adult animals also did not alter the level of bacteria adhered per enterocyte. These results suggest an age-dependent, postnatal development of available receptors forS. typhimuriumon rat enterocytes. The acquisition of these receptors is not affected by mother's milk and is unaltered by early weaning. (Pediatr Res24: 508–511, 1988)

ISSN:0031-3998    

出版商:OVID    

年代:1988

数据来源: OVID